NAME¶

std::reverse_iterator::operator[] - std::reverse_iterator::operator[]

Synopsis¶

/*unspecified*/ operator[]( difference_type n ) const; (until C++17)
constexpr /*unspecified*/ operator[]( difference_type n ) const; (since C++17)

Returns a reference to the element at specified relative location.

Parameters¶

n - position relative to current location.

Return value¶

A reference to the element at relative location, that is, base()[-n-1].

Example¶

// Run this code

#include <array>
#include <cstddef>
#include <iostream>
#include <iterator>
#include <list>
#include <vector>

int main()
{
{
int a[]{0, 1, 2, 3};
std::reverse_iterator<int*> iter{std::rbegin(a)};
for (std::size_t i{}; i != std::size(a); ++i)
std::cout << iter[i] << ' '; // decltype(iter[i]) is `int&`
std::cout << '\n';
}
{
std::vector v{0, 1, 2, 3};
std::reverse_iterator<std::vector<int>::iterator> iter{std::rbegin(v)};
for (std::size_t i{}; i != std::size(v); ++i)
std::cout << iter[i] << ' '; // decltype(iter[i]) is `int&`
std::cout << '\n';
}
{
// constexpr context
constexpr static std::array<int, 4> z{0, 1, 2, 3};
constexpr std::reverse_iterator<decltype(z)::const_iterator> it{std::crbegin(z)};
static_assert(it[1] == 2);
}
{
std::list li{0, 1, 2, 3};
std::reverse_iterator<std::list<int>::iterator> iter{std::rbegin(li)};
*iter = 42; // OK
// iter[0] = 13; // compilation error ~ the underlying iterator
// does not model the random access iterator
}
}

Output:¶

3 2 1 0
3 2 1 0

See also¶

operator* accesses the pointed-to element
operator-> (public member function)